The Academy's Evolution Site
Biology is one of the most central concepts in biology. The Academies are committed to helping those who are interested in science to learn about the theory of evolution and how it is incorporated in all areas of scientific research.
This site provides teachers, students and general readers with a range of learning resources on evolution. It includes key video clip from NOVA and WGBH produced science programs on DVD.
Tree of Life
The Tree of Life, an ancient symbol, symbolizes the interconnectedness of all life. It is an emblem of love and unity across many cultures. It also has practical applications, such as providing a framework for understanding the evolution of species and how they respond to changing environmental conditions.
The earliest attempts to depict the biological world focused on separating species into distinct categories that had been distinguished by their physical and metabolic characteristics1. These methods, based on sampling of different parts of living organisms or small fragments of their DNA, significantly increased the variety that could be included in a tree of life2. However the trees are mostly composed of eukaryotes; bacterial diversity is not represented in a large way3,4.
By avoiding the need for direct observation and experimentation, genetic techniques have enabled us to depict the Tree of Life in a more precise manner. We can construct trees using molecular methods, such as the small-subunit ribosomal gene.
Despite the rapid growth of the Tree of Life through genome sequencing, a lot of biodiversity awaits discovery. This is particularly true for microorganisms, which can be difficult to cultivate and are usually only present in a single specimen5. Recent analysis of all genomes has produced a rough draft of a Tree of Life. This includes a wide range of archaea, bacteria, and other organisms that have not yet been isolated, or whose diversity has not been fully understood6.
The expanded Tree of Life can be used to evaluate the biodiversity of a specific region and determine if certain habitats require special protection. This information can be used in a variety of ways, from identifying new treatments to fight disease to improving crops. This information is also useful for conservation efforts. It helps biologists determine the areas that are most likely to contain cryptic species that could have important metabolic functions that may be at risk from anthropogenic change. While conservation funds are important, the best way to conserve the world's biodiversity is to empower more people in developing countries with the information they require to take action locally and encourage conservation.
Phylogeny
A phylogeny (also called an evolutionary tree) depicts the relationships between organisms. Scientists can create a phylogenetic diagram that illustrates the evolutionary relationship of taxonomic groups based on molecular data and morphological similarities or differences. Phylogeny is crucial in understanding biodiversity, evolution and genetics.
A basic phylogenetic Tree (see Figure PageIndex 10 Determines the relationship between organisms that have similar characteristics and have evolved from an ancestor with common traits. These shared traits may be homologous, or analogous. Full Content are similar in their evolutionary roots and analogous traits appear similar, but do not share the same origins. Scientists group similar traits together into a grouping known as a clade. For instance, all of the species in a clade have the characteristic of having amniotic eggs. They evolved from a common ancestor which had these eggs. A phylogenetic tree can be constructed by connecting the clades to determine the organisms that are most closely related to each other.
For a more precise and accurate phylogenetic tree, scientists use molecular data from DNA or RNA to determine the relationships among organisms. This data is more precise than morphological information and provides evidence of the evolution history of an organism or group. The analysis of molecular data can help researchers identify the number of species who share a common ancestor and to estimate their evolutionary age.
The phylogenetic relationships of organisms are influenced by many factors, including phenotypic plasticity an aspect of behavior that alters in response to specific environmental conditions. This can cause a particular trait to appear more similar in one species than another, obscuring the phylogenetic signal. This problem can be mitigated by using cladistics, which incorporates the combination of homologous and analogous features in the tree.
In addition, phylogenetics can help predict the duration and rate of speciation. This information can help conservation biologists decide which species to protect from extinction. In the end, it's the conservation of phylogenetic diversity that will result in an ecosystem that is complete and balanced.
Evolutionary Theory
The main idea behind evolution is that organisms change over time as a result of their interactions with their environment. A variety of theories about evolution have been proposed by a wide variety of scientists including the Islamic naturalist Nasir al-Din al-Tusi (1201-1274) who believed that an organism would evolve slowly in accordance with its needs, the Swedish botanist Carolus Linnaeus (1707-1778) who conceived the modern hierarchical taxonomy, as well as Jean-Baptiste Lamarck (1744-1829) who suggested that the use or non-use of traits can cause changes that can be passed on to the offspring.
In the 1930s and 1940s, theories from various fields, including genetics, natural selection and particulate inheritance - came together to form the current evolutionary theory, which defines how evolution occurs through the variation of genes within a population and how these variants change over time due to natural selection. This model, which is known as genetic drift, mutation, gene flow and sexual selection, is a cornerstone of modern evolutionary biology and can be mathematically described.
Recent developments in the field of evolutionary developmental biology have revealed how variation can be introduced to a species by mutations, genetic drift and reshuffling of genes during sexual reproduction and migration between populations. These processes, along with others such as directionally-selected selection and erosion of genes (changes in the frequency of genotypes over time) can result in evolution. Evolution is defined as changes in the genome over time and changes in the phenotype (the expression of genotypes in individuals).
Incorporating evolutionary thinking into all aspects of biology education could increase student understanding of the concepts of phylogeny and evolutionary. A recent study conducted by Grunspan and colleagues, for example demonstrated that teaching about the evidence supporting evolution increased students' acceptance of evolution in a college biology class. For more details on how to teach about evolution read The Evolutionary Potency in All Areas of Biology or Thinking Evolutionarily A Framework for Infusing Evolution into Life Sciences Education.
Evolution in Action
Traditionally, scientists have studied evolution through studying fossils, comparing species and studying living organisms. Evolution is not a past moment; it is an ongoing process that continues to be observed today. The virus reinvents itself to avoid new antibiotics and bacteria transform to resist antibiotics. Animals adapt their behavior in the wake of the changing environment. The resulting changes are often easy to see.
It wasn't until late 1980s that biologists began to realize that natural selection was also at work. The key is the fact that different traits confer a different rate of survival as well as reproduction, and may be passed down from one generation to another.
In the past, if one allele - the genetic sequence that determines colour - appeared in a population of organisms that interbred, it might become more common than any other allele. As time passes, this could mean that the number of moths that have black pigmentation could increase. The same is true for many other characteristics--including morphology and behavior--that vary among populations of organisms.
Monitoring evolutionary changes in action is much easier when a species has a fast generation turnover, as with bacteria. Since 1988 the biologist Richard Lenski has been tracking twelve populations of E. bacteria that descend from a single strain; samples from each population are taken on a regular basis, and over 50,000 generations have now been observed.
Lenski's research has shown that a mutation can profoundly alter the efficiency with the rate at which a population reproduces, and consequently the rate at which it evolves. It also shows that evolution takes time, which is hard for some to accept.
Microevolution is also evident in the fact that mosquito genes for pesticide resistance are more prevalent in areas that have used insecticides. That's because the use of pesticides creates a pressure that favors those with resistant genotypes.
The rapidity of evolution has led to a greater appreciation of its importance especially in a planet that is largely shaped by human activity. This includes the effects of climate change, pollution and habitat loss that prevents many species from adapting. Understanding 에볼루션 코리아 can help us make smarter decisions regarding the future of our planet and the lives of its inhabitants.